From: Vineet Gupta <vgupta@xxxxxxxxxxxx>
commit 8c42a5c02bec6c7eccf08957be3c6c8fccf9790b upstream.
commit feb92d7d3813456c11dce21 "(ARC: perf: don't bail setup if pct irq
missing in device-tree)" introduced a silly brown-paper bag bug:
The assignment and comparison in an if statement were not bracketed
correctly leaving the order of evaluation undefined.
|
| if (has_interrupts && (irq = platform_get_irq(pdev, 0) >= 0)) {
| ^^^ ^^^^
And given such a chance, the compiler will bite you hard, fully entitled
to generating this piece of beauty:
|
| # if (has_interrupts && (irq = platform_get_irq(pdev, 0) >= 0)) {
|
| bl.d @platform_get_irq <-- irq returned in r0
|
| setge r2, r0, 0 <-- r2 is bool 1 or 0 if irq >= 0 true/false
| brlt.d r0, 0, @.L114
|
| st_s r2,[sp] <-- irq saved is bool 1 or 0, not actual return val
| st 1,[r3,160] # arc_pmu.18_29->irq <-- drops bool and assumes 1
|
| # return __request_percpu_irq(irq, handler, 0,
|
| bl.d @__request_percpu_irq;
| mov_s r0,1 <-- drops even bool and assumes 1 which fails
With the snafu fixed, everything is as expected.
| bl.d @platform_get_irq <-- returns irq in r0
|
| mov_s r2,r0
| brlt.d r2, 0, @.L112
|
| st_s r0,[sp] <-- irq isaved is actual return value above
| st r0,[r13,160] #arc_pmu.18_27->irq
|
| bl.d @__request_percpu_irq <-- r0 unchanged so actual irq returned
| add r4,r4,r12 #, tmp363, __ptr
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arc/kernel/perf_event.c | 29 +++++++++++++++++++----------
1 file changed, 19 insertions(+), 10 deletions(-)
--- a/arch/arc/kernel/perf_event.c
+++ b/arch/arc/kernel/perf_event.c
@@ -562,7 +562,7 @@ static int arc_pmu_device_probe(struct p
{
struct arc_reg_pct_build pct_bcr;
struct arc_reg_cc_build cc_bcr;
- int i, has_interrupts, irq;
+ int i, has_interrupts, irq = -1;
int counter_size; /* in bits */
union cc_name {
@@ -637,18 +637,27 @@ static int arc_pmu_device_probe(struct p
.attr_groups = arc_pmu->attr_groups,
};
- if (has_interrupts && (irq = platform_get_irq(pdev, 0) >= 0)) {
+ if (has_interrupts) {
+ irq = platform_get_irq(pdev, 0);
+ if (irq >= 0) {
+ int ret;
+
+ arc_pmu->irq = irq;
+
+ /* intc map function ensures irq_set_percpu_devid() called */
+ ret = request_percpu_irq(irq, arc_pmu_intr, "ARC perf counters",
+ this_cpu_ptr(&arc_pmu_cpu));
+
+ if (!ret)
+ on_each_cpu(arc_cpu_pmu_irq_init, &irq, 1);
+ else
+ irq = -1;
+ }
- arc_pmu->irq = irq;
-
- /* intc map function ensures irq_set_percpu_devid() called */
- request_percpu_irq(irq, arc_pmu_intr, "ARC perf counters",
- this_cpu_ptr(&arc_pmu_cpu));
+ }
- on_each_cpu(arc_cpu_pmu_irq_init, &irq, 1);
- } else {
+ if (irq == -1)
arc_pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;
- }
/*
* perf parser doesn't really like '-' symbol in events name, so let's
